Line-strength and color comparison. Observed (horizontal axes) line-strength and colors are compared to the predicted values (vertical axes) using the FASTAR (blue filled circles) and MILES (orange squares) interpolators. From left to right, we show the behavior of the metallicity-sensitive [MgFe]’ (Thomas et al. 2003), the age-sensitive H_βO (Cervantes & Vazdekis 2009), and the IMF-sensitive TiO₂ (Faber et al. 1985; Trager et al. 1998). The panel on the right shows the comparison of the (g − r) color. The interpolation in FASTAR tends to outperform that of MILES, with systematically smaller residuals as indicated on the bottom right corner of each panel.